CN103090973B - Ia type diamond color quick grading method based on spectrum - Google Patents

Abstract

The invention discloses an Ia type diamond color quick grading method based on a spectrum. The Ia type diamond color quick grading method based on the spectrum comprises that balanced compound light is emitted on a to-be detected diamond, and the compound light which is reflected through the to-be detected diamond is collected through an integrating sphere. After the light collected by the integrating sphere is split, a charge coupled device (CCD) detector is used for detecting so as to obtain a reflectance spectrum of the to-be detected diamond. After the reflectance spectrum of the to-be detected diamond is uniformized, a nitrogen absorption band is selected from the uniformized reflectance spectrum, and then the area of the nitrogen absorption band is calculated. Compared the area of the nitrogen absorption band with a standard threshold value file, the color of the to-be detected diamond is graded. According to the Ia type diamond color quick grading method based on the spectrum, the nitrogen absorption band is selected from the reflectance spectrum of the collected to-be detected diamond and the area of the nitrogen absorption band is calculated, then the area of the nitrogen absorption band is compared with the standard threshold value file, and so that the grading of the color of the diamond is achieved. The Ia type diamond color quick grading method based on the spectrum is simple in operation, quick and accurate in testing, high in consistency and capable of being widely used in the jewelry identification industry.

Description

Based on the Ia type diamond color rapid classification method of spectrum

Technical field

The present invention relates to gemstone testing field, particularly based on the Ia type diamond color rapid classification method of spectrum.

Background technology

The chemical composition of diamond is carbon (C) element, and its crystal structure is the tetrahedron that 4 carbon atoms are formed.Pure diamond is water white, but all contains the impurity element of trace in the rough diamond of the overwhelming majority.According to analysis, the massfraction of C in diamond can reach 99.95%, and its submember has the impurity such as N, B, H.According to whether obviously there is nitrogen, diamond being divided into two types, nitrogenous diamond being called I type diamond, the diamond not containing the obvious nitrogen of quantity is called II type diamond.

When the harsh one-tenth of diamond, intracrystalline nitrogen element exists with monoatomic discrete state.Under very long geochronic High Temperature High Pressure effect, the single nitrogen-atoms in diamond crystal condenses together gradually and forms the condensate of nitrogen-atoms.The condensate of nitrogen-atoms may be the condensate of 2,3 or 4 nitrogen-atoms, also may be more.There is the polymeric diamond of nitrogen-atoms and belong to Ia type diamond.Ia type diamond accounts for the overwhelming majority of rough diamond, accounts for 98%.The color of Ia type diamond is relevant with nitrogen content, and when nitrogen content is extremely low, diamond is colourless, and the saturation degree of the higher yellow of nitrogen content is higher.

In current gemstone testing industry, the grade scale that the mechanisms such as main employing American Gem institute (GIA) and International Jewelry federation (CIBJO) formulate carries out classification to the color of diamond, for colourless---light yellow series (cape series) diamond, 23 grades such as D-Z can be divided into or directly adopt words such as " extremely white, excellent white, white, pale yellow white " directly to describe, and domestic qualification generally divides 11 grades such as D-N, while adopting letter representation, also adopt percentage method for making numeral.Qualification now to diamond color, mainly adopt than colored stone control methods, tested diamond is contrasted with the standard colorimetric stone having demarcated color grade under light source, by eye-observation, selects and the grade of the grade of tested diamond color immediate standard colorimetric stone as tested diamond.But, adopt the method for eye-observation contrast, not only expend time in length, and the judgement of color grade because being subject to light source, background tone, diamond size, cut, naked eyes reduce accuracy to the impact of the factor such as color recognition capability, also cannot reach the consistance of color grading simultaneously.

Summary of the invention

In order to solve the above-mentioned technical matters existed in diamond color classification, the object of this invention is to provide a kind of simple to operate, quick, accurate and Ia type diamond color rapid classification method based on spectrum that consistance is high.

The technical solution adopted for the present invention to solve the technical problems is:

Based on the Ia type diamond color rapid classification method of spectrum, comprising:

S1, the complex light of equilibrium is irradiated on tested diamond;

S2, use integrating sphere collect the complex light reflected through tested diamond;

After S3, the light collected integrating sphere carry out light splitting, use ccd detector to detect, and then obtain the reflectance spectrum of tested diamond;

S4, the reflectance spectrum of tested diamond is normalized after, choose nitrogen absorption band from normalized reflectance spectrum, then calculate the area of nitrogen absorption band;

S5, the area of nitrogen absorption band and level threshold value file to be compared, color grading is carried out to tested diamond.

Further, described in described step S5, the process of establishing of level threshold value file is as follows:

SS1, obtain according to step S1 to S3 the standard colorimetric stone of each color grade reflectance spectrum and after being normalized, choose nitrogen absorption band from normalized reflectance spectrum;

SS2, adopt the area of following formulae discovery nitrogen absorption band, and then area threshold corresponding to the standard colorimetric stone obtaining each color grade is interval, finally according to the interval Criterion threshold file of the area threshold that the standard colorimetric stone of all colours grade is corresponding:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.

Further, described standard colorimetric stone comprises standard max and compares colored stone than colored stone or standard min.

Further, the interval standard max by this grade of the area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the area of nitrogen absorption band of colored stone and the standard max of the lower level of this grade;

Or,

The interval standard min by this grade of area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the standard min of the area of the nitrogen absorption band of colored stone and a upper grade of this grade.

Further, described step S4, it is specially:

After the reflectance spectrum of tested diamond is normalized, choose nitrogen absorption band from normalized reflectance spectrum, then adopt the area of following formulae discovery nitrogen absorption band:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.

Further, described step S5, it is specially:

The area of nitrogen absorption band and level threshold value file are compared, the color grade of the standard colorimetric stone corresponding to the area threshold interval residing for the area of this nitrogen absorption band is defined as the color grade of tested diamond.

Further, be normalized the reflectance spectrum of tested diamond described in described step S4, it is specially:

Selected suitable wavelength, as normalization reference point, is normalized the reflectance spectrum of tested diamond.

The invention has the beneficial effects as follows: the Ia type diamond color rapid classification method based on spectrum of the present invention, the complex light of balance is irradiated on tested diamond, then by integrating sphere collection after the light that tested diamond reflects, carry out light splitting, and then adopt ccd detector to detect, and then obtain the reflectance spectrum of tested diamond, after this reflectance spectrum is normalized, choose nitrogen absorption band and calculate the area of nitrogen absorption band, then the area of nitrogen absorption band and level threshold value file are compared, thus realize the color grading of diamond, not only simple to operate, test fast and accurately, and consistance is high.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described.

Fig. 1 is the process flow diagram of the Ia type diamond color rapid classification method based on spectrum of the present invention;

Fig. 2 is the structured flowchart carrying out a specific embodiment of spectra collection of the Ia type diamond color rapid classification method based on spectrum of the present invention;

Fig. 3 is the reflected light spectrogram adopting the standard colorimetric stone of the test D-N of the Ia type diamond color rapid classification method based on spectrum of the present invention totally 11 grades to obtain;

Fig. 4 is the spectrogram obtained after being normalized the reflected light spectrogram in Fig. 3;

Fig. 5 be to normalization in Fig. 4 after reflected light spectrogram in the spectrogram of H grade choose the schematic diagram of nitrogen absorption band;

Fig. 6 is the schematic diagram that the reflectance spectrum to tested diamond of the Ia type diamond color rapid classification method based on spectrum of the present invention carries out fluorescence Processing for removing.

Embodiment

For the ease of following description, first provide following explanation of nouns:

CCD:Charge-coupled Device, charge coupled cell, directly can be converted to analog electrical signal by optical signalling.

With reference to Fig. 1, the invention provides a kind of Ia type diamond color rapid classification method based on spectrum, comprising:

S1, the complex light of equilibrium is irradiated on tested diamond;

S2, use integrating sphere collect the complex light reflected through tested diamond;

After S3, the light collected integrating sphere carry out light splitting, use ccd detector to detect, and then obtain the reflectance spectrum of tested diamond;

S4, the reflectance spectrum of tested diamond is normalized after, choose nitrogen absorption band from normalized reflectance spectrum, then calculate the area of nitrogen absorption band;

S5, the area of nitrogen absorption band and level threshold value file to be compared, color grading is carried out to tested diamond.

Obvious, in above-mentioned steps S3, after using ccd detector to detect, after also needing to carry out the operations such as signal conversion, just obtain the reflectance spectrum of tested spectrum, be not described in detail here.

With reference to Fig. 2, the specific embodiment carrying out spectra collection is as follows: the complex light of balance is incided integrating sphere S by the entrance port 1 of integrating sphere S inner, complex light in integrating sphere S directly or be irradiated to after diffuse reflection be placed on sample port 2 place tested diamond 3 on and reflect, the complex light of then being collected by integrating sphere S by thief hatch 4 is transferred to beam splitting system 6 by optical fiber 5 and carries out light splitting, CCD detecting device 7 is used to detect the light collected afterwards, after last usage data processing module 8 carries out data processing to the value detected, obtain the reflectance spectrum of tested diamond 3.

Here, complex light also can shine directly into tested diamond 3 from the top of tested diamond 3, then adopts the collection light that uses the same method, and finally obtains the reflectance spectrum of tested diamond 3.

Be further used as preferred embodiment, described in described step S5, the process of establishing of level threshold value file is as follows:

SS1, obtain according to step S1 to S3 the standard colorimetric stone of each color grade reflectance spectrum and after being normalized, choose nitrogen absorption band from normalized reflectance spectrum;

SS2, adopt the area of following formulae discovery nitrogen absorption band, and then area threshold corresponding to the standard colorimetric stone obtaining each color grade is interval, finally according to the interval Criterion threshold file of the area threshold that the standard colorimetric stone of all colours grade is corresponding:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.λ ₀refer to the arbitrary wavelength of the reflectance spectrum of tested diamond in the wave band of light intensity smooth variation.λ ₁, λ ₂be the wavelength value preset, reflectance spectrum is at λ ₁with λ ₂between part be nitrogen absorption band.

Be further used as preferred embodiment, described standard colorimetric stone comprises standard max and compares colored stone than colored stone or standard min.

Be further used as preferred embodiment, the interval standard max by this grade of area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the area of nitrogen absorption band of colored stone and the standard max of the lower level of this grade;

Or,

The interval standard min by this grade of area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the standard min of the area of the nitrogen absorption band of colored stone and a upper grade of this grade.

Be further used as preferred embodiment, described step S4, it is specially:

After the reflectance spectrum of tested diamond is normalized, choose nitrogen absorption band from normalized reflectance spectrum, then adopt the area of following formulae discovery nitrogen absorption band:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.λ refers to the wavelength value at arbitrary place in spectrum in this application, refers in particular to the wavelength value at any place in the absorption band of nitrogen in this formula.

λ ₀refer to the arbitrary wavelength of the reflectance spectrum of tested diamond in the wave band of light intensity smooth variation, can think that the light intensity at this wavelength place is the maximum light intensity of denitrogenating outside absorption band, consistent with standard colorimetric stone spectral normalization reference point.Here, in order to maintain the consistance of color grading, once a selected wavelength value is as normalization reference point, when carrying out spectral normalization to the reflectance spectrum of other tested diamond, also adopt this wavelength value as normalization reference point.

Be further used as preferred embodiment, described step S5, it is specially:

The area of nitrogen absorption band and level threshold value file are compared, the color grade of the standard colorimetric stone corresponding to the area threshold interval residing for the area of this nitrogen absorption band is defined as the color grade of tested diamond.

Color is more shallow or connect subdiaphanous diamond, and by the mode of human eye contrast than colored stone, be difficult to accurately carry out color grading, the present invention, according to the distribution of nitrogen content, can carry out color grading more exactly, eliminates the impact of human eye.Here, the area of nitrogen content value nitrogen absorption band characterizes.Therefore here according to the area of the nitrogen absorption band of the reflectance spectrum of the standard colorimetric stone of each grade of calculating, and then obtain each grade standard colorimetric stone area threshold interval after Criterion threshold file, promptly can carry out color grading according to the reflectance spectrum of the tested diamond of collection of the present invention.

Because standard colorimetric stone is all complete use, for a set of standard max than colored stone or a set of standard min than colored stone, therefore, area threshold interval also divide use standard max than colored stone with standard min than colored stone two kinds of situations.The standard max of each grade is the minimum value in the area threshold interval of this grade than the area value of the nitrogen absorption band of colored stone, and accordingly, the standard min of each grade is the maximal value in the area threshold interval of this grade than the area value of the nitrogen absorption band of colored stone.The preferential selection standard lower limit of the present invention compares colored stone, namely the standard min of each grade is respectively maximal value and the minimum value of this grade than the area value of the nitrogen absorption band of colored stone than the standard min of the area value of the nitrogen absorption band of colored stone and a upper grade of this grade, thus the area threshold defining this grade is interval.Domesticly be generally D-N totally 11 grades, here, grade is followed successively by D, E, F, G, H, I, J, K, L, M, N from high to low.Namely D grade is a upper grade of E grade, and E grade is a upper grade of F grade.Such as, standard min is adopted to compare colored stone, the area value of the nitrogen absorption band that the standard min of E grade is more corresponding than colored stone is 1000, the area value of the nitrogen absorption band that the standard min of D grade is more corresponding than colored stone is 800, then the area threshold interval of E grade is 800-1000, when the area value of the nitrogen absorption band obtaining certain tested diamond is 900, judge that the grade of this tested diamond is as E grade.

Be further used as preferred embodiment, be normalized the reflectance spectrum of tested diamond described in described step S4, it is specially:

Selected suitable wavelength, as normalization reference point, is normalized the reflectance spectrum of tested diamond.The formula that normalized uses is:

$R_{\mathrm{\λ}}=R_{\mathrm{\λ}}^{\′}\×\frac{100\%}{R_{{\mathrm{\λ}}_0}^{\′}}$

Wherein, suitable wavelength and λ above ₀define identical, refer to the arbitrary wavelength of the reflectance spectrum of tested diamond in the wave band of light intensity smooth variation, can think that the light intensity at this wavelength place is the maximum light intensity (because without absorbing, therefore reflectivity is maximal value, thus light intensity is also maximal value) of denitrogenating outside absorption band; for the reflectance spectrum before normalization is λ at wavelength ₀the reflectivity at place, R ' _λrefer to that the reflectance spectrum before normalization is the reflectivity at λ place at wavelength, R _λrefer to that the reflectance spectrum after normalization is the reflectivity at λ place at wavelength, the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place is

Such as, in figure 3, the suitable wavelength as normalization reference point can be reflectance spectrum any one wavelength value in 500nm-700nm wave band of tested diamond, when being normalized the reflectance spectrum of Fig. 3, and λ ₀selected wavelength is 600nm.Here, in order to maintain the consistance of color grading, once a selected wavelength value is as normalization reference point, when carrying out middle-low alloy steels to the reflectance spectrum of other tested diamond, also adopt this wavelength value as normalization reference point.Fig. 3 is the reflected light spectrogram adopting the standard colorimetric stone of method of the present invention test D-N grade to obtain, choose the reflected light spectrogram that obtains after 600nm is normalized as normalization reference point as shown in Figure 4, the curve in Fig. 4 is followed successively by the reflected light spectrogram after the normalization of the reflected light spectrogram of the standard colorimetric stone of D-N level from top to bottom.The reflected light spectrogram choosing H grade is example, and the area of the nitrogen absorption band chosen from the reflectance spectrum after normalization is as shown in dash area in Fig. 5.

The reflectance spectrum of part diamond sample there will be fluorescence interference, therefore needs to carry out fluorescence Processing for removing, namely between described step S3 and S4, also comprises step:

S34, fluorescence Processing for removing is carried out to the reflectance spectrum of tested diamond: the reflectance spectrum of tested diamond is processed, after isolating fluorescence signal, the reflectance spectrum after the fluorescence that is eliminated.

With reference to Fig. 6, isolate fluorescence signal from the reflectance spectrum of tested diamond after, the reflectance spectrum after the fluorescence that is eliminated, the reflectance spectrum after can eliminating according to fluorescence calculates the area of nitrogen absorption band.

In Ia type diamond, because the condensate of nitrogen-atoms may be the condensate of 2,3 or 4 nitrogen-atoms, also may be more, the condensate of 2 nitrogen-atoms, the absorption peak of its nitrogen is at 452nm, 465nm and 478nm place; The condensate of 3 nitrogen-atoms, the absorption peak of its nitrogen is at 415nm place; The condensate of 4 nitrogen-atoms, the absorption peak of its nitrogen is at 300nm place.The color of Ia type diamond is mainly by the impact of Nitrogen Impurities content in diamond, and therefore, the present invention can carry out diamond color classification according to the method for the area of the nitrogen absorption band near the absorption peak of the nitrogen of computational reflect spectrum.

More than that better enforcement of the present invention is illustrated, but the invention is not limited to described embodiment, those of ordinary skill in the art also can make all equivalent variations or replacement under the prerequisite without prejudice to spirit of the present invention, and these equivalent modification or replacement are all included in the application's claim limited range.

Claims (6)

1., based on the Ia type diamond color rapid classification method of spectrum, it is characterized in that, comprising:

S1, the complex light of equilibrium is irradiated on tested diamond;

S2, use integrating sphere collect the complex light reflected through tested diamond;

After S3, the light collected integrating sphere carry out light splitting, use ccd detector to detect, and then obtain the reflectance spectrum of tested diamond;

S4, selected suitable wavelength, as normalization reference point, after being normalized, are chosen nitrogen absorption band from normalized reflectance spectrum, then calculate the area of nitrogen absorption band to the reflectance spectrums of tested diamond;

S5, the area of nitrogen absorption band and level threshold value file to be compared, color grading is carried out to tested diamond.

2. the Ia type diamond color rapid classification method based on spectrum according to claim 1, it is characterized in that, described in described step S5, the process of establishing of level threshold value file is as follows:

SS1, obtain according to step S1 to S3 the standard colorimetric stone of each color grade reflectance spectrum and after being normalized, choose nitrogen absorption band from normalized reflectance spectrum;

SS2, adopt the area of following formulae discovery nitrogen absorption band, and then area threshold corresponding to the standard colorimetric stone obtaining each color grade is interval, finally according to the interval Criterion threshold file of the area threshold that the standard colorimetric stone of all colours grade is corresponding:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.

3. the Ia type diamond color rapid classification method based on spectrum according to claim 2, it is characterized in that, described standard colorimetric stone comprises standard max and compares colored stone than colored stone or standard min.

4. the Ia type diamond color rapid classification method based on spectrum according to claim 3, it is characterized in that, the interval standard max by this grade of area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the area of nitrogen absorption band of colored stone and the standard max of the lower level of this grade;

Or,

The interval standard min by this grade of area threshold that the standard colorimetric stone of described each color grade is corresponding is formed than the area of the nitrogen absorption band of colored stone than the standard min of the area of the nitrogen absorption band of colored stone and a upper grade of this grade.

5. the Ia type diamond color rapid classification method based on spectrum according to claim 4, it is characterized in that, described step S4, it is specially:

After the reflectance spectrum of tested diamond is normalized, choose nitrogen absorption band from normalized reflectance spectrum, then adopt the area of following formulae discovery nitrogen absorption band:

$S=\underset{{\mathrm{\λ}}_1}{\overset{{\mathrm{\λ}}_2}{\∫}}100\×(R_{{\mathrm{\λ}}_0}-R_{\mathrm{\λ}})\mathrm{d\λ}$

Wherein, λ ₁, λ ₂refer to the wavelength at nitrogen absorption band two ends place, λ ₀for normalization reference point, for the reflectance spectrum after normalization is λ at wavelength ₀the reflectivity at place, r _λfor the reflectivity that the reflectance spectrum after normalization is λ place at wavelength, S is the area of nitrogen absorption band.

6. the Ia type diamond color rapid classification method based on spectrum according to claim 5, it is characterized in that, described step S5, it is specially:

The area of nitrogen absorption band and level threshold value file are compared, the color grade of the standard colorimetric stone corresponding to the area threshold interval residing for the area of this nitrogen absorption band is defined as the color grade of tested diamond.